(CNN) --Terrorists stormed past security guards into an affluent, heavily secured residential neighborhood in the Saudi capital Saturday and set off three explosions, journalists and officials in Riyadh said.

The attack came one day after the U.S. Embassy announced it would close temporarily over concerns of rising terror threats.

A senior official in the Saudi Interior Ministry said his government was certain the attack was planned and carried out by al Qaeda using the same suicide car bombing strategy employed in the May 12 attacks in Riyadh.

The triple bombings in May targeted apartment complexes housing Westerners. Those bombings left 23 people dead, including nine Americans. Twelve bombers were also killed.

Although the Saudi official confirmed two dead and another 87 wounded Saturday, diplomatic sources said as many as 28 people were killed and 100 wounded -- many of them children -- in the complex targeted.

According to reports, the attackers first fired on security guards and then drove their explosives-laden cars through the gates.

At least two dozen ambulances rushed to the Al-Muhaya compound -- villas housing several hundred residents -- where a large plume of smoke was seen, journalists said.

No U.S. government officials live in the compound, which lies about three miles from the U.S. Embassy in western Riyadh.

One U.S. citizen was wounded and another is unaccounted for after the attack, an embassy official told CNN.

The wounded American -- who was registered with the embassy -- was being treated at a hospital, but a condition report was not immediately available.

The blasts ripped through a complex housing mainly Arabs.

Hanadi Fundouqli, manager of the Al-Muhaya compound, said all but four of the residents are Arabs. The four are from Italy, Germany, and France, she said.

Saudi business sources told CNN the compound was about a mile from the homes of several top members of Saudi Arabia's ruling family.

The explosions happened about midnight, a time when many of the adult residents were away from their homes because of Ramadan observances, leaving a large number of children in the compound, Fundouqli said.

Raid Qusti, Riyadh bureau chief for the Arab News daily newspaper, said he heard a blast, then ambulance and police sirens. He added that witnesses reported hearing gunfire before the explosion.

The U.S. Embassy and consulates in Saudi Arabia said Friday that they would be closed Saturday to at least Monday because of concerns that terrorists were planning an attack in the kingdom.

An advisory released Friday by the U.S. Embassy in Riyadh said the embassy "continues to receive credible information that terrorists in Saudi Arabia have moved from the planning to operational phase of planned attacks in the kingdom."

Before the explosion Saturday, the British Embassy in Bahrain warned its personnel of the threat of a terror attack. Bahrain is an island nation in the Persian Gulf, east of Saudi Arabia.

The U.S. State Department's closures affect the U.S. Embassy in Riyadh and consulates in Jeddah and Dhahran.